Retort



June 24. 1924. 1,498;635

4 F. J. METZGER REToR'r 'filed Aug. 4, 1923 n -INVENTOR A. ATTORNEYS Patented June 24, i924.

UNITED STATES FLOYD J. METZGER, or NEW YORK, N. Y.,

ASSIGNOR '1"0` CALIFORNIA CYANIDE COM- PANY, INCORPORATED, O'F NEW YORK, N. Y., A CORPORATION 0F DELAWARE.

'RETORR Application filed August 4, 1923. Serial No. 655,643.

To all whom t may concern.'

Be it known that I, FLOYD J. METZGER, a citizen of the United States, residing at New York city, in the county of New York, State of New York, have invented certain new and useful Improvements in Retorts; and I do hereby declare the following to be a full, clear, and exact description of the A method of-l'ixing nitrogen is described in United States Letters Patent No. 1,322,- 195 and involves the heating lof mixtures of alkali metal carbonatesv or oxides with carbon and relatively small amounts of iron, preferably in the form of iron oxide, in the presence of nitrogenous gas. lAs little as two per cent of iron is effective and small amounts are used to avoid filling the reaction chamber with material which does not enter into the composition of the resulting cyanide material. This cyanide material or furnace product containing cyanide is treated after removal from the retort to recover cyanide or hydrocyanic acid. This may be accomplished by leaching the furnace product or by treating it with carbon dioxide or other suitable agents, for ex-A ample, with steam, to convert the cyanide into ammonia.

Oxygen or oxidizingr agents convert cyanide at low temperatures into cyanate which is not a desirable product. llikt-high temperatures such as arepresent in the ref action zone and particularly in the presenceV of carbon, this undesirable oxidation is avoided. Heretofore much difficulty Vhas been experienced in avoiding 4the production of cyanate because the retorts used were so constructed that after the reaction the furnace product `passed into a zone of low temperature where oxidation was pos-V sible. Consequently ithas been considered necessary to employ nitrogenous gases from 'which oxygen and oxidizing agents have been substantially removed.

It is the object of the present invention to provide a retort in which the cyanide reaction may be carried on with nitrogenous gases containing oxygen or oxidizing agents witliout'danger ofloss of cyanide by conversion into cyanate.

Further objects and advantages of the invention will be understood by reference to the following specification and the accompanying drawing in which a retort einbodying the invention is diagrammatically illustrated.

The' object of the invention may be accomplished by the provision of a retort which is adapted to be supported in a suitable furnace and is provided with means to hold the material in the reaction zone and at the temperature thereof until the reaction is completed. The meansr employed should prevent contact'of the furnace product with the nitrogenous gases used at a temperature lowerthan that at which the reaction is conducted. Provision should likewise be made for the withdrawal of the furnace product at the conclusion of the reaction.V To best meet these requirements an inclined retort is used, the retort being mounted in the furnace and arranged so that it may be rotated. At the lower end of the retort a plug or plunger is introduced at a point Vsubstantially corresponding with the wall of the surrounding furnace. This plunger prevents descent of the furnace product `beyond the heating zone and is provided with an inlet whereby the nitrogenous gas may be introduced to the retort. The plunger is connected preferably to the closure at the end of the retort so that upon removal of the latter the plunger may be withdrawn, thus permitting a portion of the contents of the retort to bc raked therefrom. Before the plunger is withdrawn the supply of nitrogenous gas is shut o. The furnace product may be raked from the retort into containers which are more or less air-tight to minimize contact of atmospheric oxygen therewith. In the operation there is no contact of the furnace product with oxygen at a temperature lower than that of the reaction for a sufficiently prolonged time to permit oxidationV and the production of cyanates.

Utilization of the retort as described per- CFT ftrogen is fixed as cyanide.

mits the `use of nitrogenous gases such as atmospheric air .and particularly of gases recovered from the combustion products of the heating furnace. These combustion products contain nitrogen, a considerable proportion of carbon dioxide and some oxygen. The combustion products are scrubbed to remove the carbon dioxide which may be utilized in the `separation of hydrocyanic acid from the furnace product. The remaining ynitrogenous -gases containing a proportion of oxygen are Vparticularly desirable for use in the cyanide reaction. By slightly increasing the proportion of carbon inthe mixture .which is fed to `the retort the presence ofoxygen :may be neutralized and preventing` contact vof vthe oxygen in the nitrogcnous gases .with the ,furnace product at a temperature lower than that of the .reaction the production of cyanate is substantially avoided.

As an example yof the Lapplication of the invention itis desirable to employ aimixture of alkali metal carbonate or oxide, carbon and iron in the relative proportions of forty parts of sodium carbonate, fifty-eight parts vof coke and a limited quantity of iron, preferably in the neighborhood of two per cent, for example, in -the yform of iron oxide. VThese materials are finely ground tand are mixed in a suitable mixingdevice to ensure thorough mingling. Aquantity of water is preferably added during the mixing but .the amount of water is limited so that the mass is not ,perceptibly moist.

The mass is dried and is then introduced into 'the :reaction chamber or retort and is there subjected to an elevated temperature ranging from 950O to 1100o C. while atmospheric air or an equivalent nitrogenous gas .is Apassed through .and in contact with the mass. The vvretort is substantially filled with the mixture ,and is rotated to ensure thoroughcontact-:of the nitrogenous gas `with all ofthe mixture with the Vresult that the Yni- The oxygen ,present combines with the excess carbon and escapes with vthe gaseous reaction products from the upper end of the retort. During `the reaction the furnace product is prevented from descending below the heating zone and is therefore continuously maintained at the temperature of the reaction. l/Vhen the reaction is completed the retort is opened .and `the plunger isV withdrawn. A portion of the charge may be raked from the retort after which the plunger' is returned ,and sufficient material is added to the retort to again substantially lill it. rlhe furnace ,product contains upward to thirty per cent .of cyanide which may be recovered or converted into useful products as hereinbefore described.

-a furnace constructed of brick-work or other `occupy an inclined position.

suitable material and preferably having a refractory lining 6 enclosinga combustion chamber 7. A suitable fuel, for example producer gas, may be supplied from agasproducer 8 through a passage 9 from which the gas is delivered through gas inlets 10 to verably passing through an economizer (not shown). `No surplus heat is employed in `preheating the air which is mixed with the gas before combustion thereof. Reference is made to Letters Patent No. 1,322,195 above referred to for the details of this arrangement.

A tube 12, preferably of oxidation-resistant `material such as .an alloy containing nickel and chromium, isdisposed in suitable openings in the walls of the furnace 5 to The rtube is provided with flanges 13 "and 14 resting on rollers 15 and 16. The flange 14 bears against a `thrust roll -1-7 which maintains the tube in proper positioninthe furnace. The tube may be -rotatedlby means of a chain 18 engaging a sprocket 19 thereon and a sprocket 20.011 a shaft 21 which may be actuated in any suitable manner.

The tube 12 is filled with a furnace mixture from the upper end which is open as indicated in the drawing. The vlower end ofthe tube ispreferably closed by a head 22 bolted or otherwise secured to a iange on the tube. To prevent the travel of the furnace 'mixture` beyond -that portion of the tubewhichis heatedby the furnace, a plun- .ger23 is provided which =is inserted in the `end ofithe tube. The plunger 23 has an extheftubeand,las vwill be apparent none ofthe material is permitted to cool below the temperature of the reaction .Zone and to contact `thereafter withnitrogenous gas during the operation of the furnace. reacting mass lsheld yatthe vmaximum tem- Thus all of ythe perature and the formation of cyanate is prevented. When the freaction is completed the head 22 and plunger 23 are removed and the furnace .product is withdrawn from the tube which is readyfor the succeeding oper- Iation. when the head and plunger Ahavebeen secured again in place.

Various changes may belmade inthe structure described without departing from the invention, it being essential only to provide means to prevent descent of the furnace product during the operation beyond the heating zone.

I claim l. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending through the chamber and means Within the retort to prevent the contents thereof from passing substantially beyond the Wall of the combustion chamber, said means having a passage to convey gas to the interior of the retort and being removable to permit WithdraWal of the contents thereof.

2. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending in an inclined position through the chamber, and means Within the retort at the lovver end thereof to prevent the contents from passing substantially beyond the Wall of the combustion chamber, said means having a passage to convey gas to the interior of the retort and being removable to permit Withdrawal of the contents thereof.

3. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending through the chamber, means for rotating the retort, means Within the retort to prevent the contents thereof from passing substantially beyond the Wall of the combustion chamber, said means having a passage to convey gas to the interior' of the retort and being removable to permit Withdrawal of the contents thereof, and stationary means to supply gas to the passage while the retort is rotating.

4. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending in an inclined position through the chamber, means for rotating the retort, means Within the retort at the lower end thereof to prevent the contents from passing substantially beyond the Wall of the combustion chamber, said means having a passage to convey gas to the interior of the retort and being removable to permit Withdrawal of the contents thereof,

and stationary means to supply gas to the passage While the retort is rotating.

5. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending through the chamber and a removable plunger Within the retort to prevent the contents thereof from passing substantially beyond the Wall of the combustion chamber, said plunger having an extension with a passage therethrough to convey gas to the interior of the retort.

6. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending through the chamber in an inclined position, and a removable plunger Within the retort at the lower end thereof to prevent the contents thereof from passing substantially beyond the Wall of the combustion chamber, said plunger having an extension With a passage therethrough to convey gas to the interior of the retort.

7. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending through the combustion chamber, means for rotating the retort, a removable plunger Within the retort to prevent the contents thereof from passing substantially beyond the wall of the combustion chamber, said plunger having an extension With a passage therethrough to convey gas to the interior of the retort and stationary means to supply gas to the passage Whilethe retort is rotating.

8. In an apparatus of the character described, a furnace having a combustion chamber, a retort extending in inclined position through the chamber, means for rotating the retort, a removable plunger at the lower end thereof to prevent the contents from passing substantially beyond the Wall of the combustion chamber, said plunger having an extension with a passage therethrough to convey gas to the interior of the retort and stationary means to supply gas to the passage While the retort is rotating.

In testimony whereof I atlix my signature.

FLOYD J. METZGER. 

